JP2743709B2 - Aluminum alloy for extrusion and forging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy having a strength comparable to a wrought alloy, and excellent in forgeability and wear resistance.

[0002]

2. Description of the Related Art Al-Mg-Si alloys in the 6000 series, such as 6061, 6066, 6082, etc., have been conventionally used as aluminum alloys for hot forging. Among them, 6061 alloy is most often used as a forging material. However, the 6061 alloy has a tensile strength of 27-
It is 33 kg / mm ^2, which is restricted to the use as a so-called medium strength member.

[0003] 6000-series aluminum alloy, after being molded to and a predetermined shape to improve the strength by hot forging, heat treatment such as T ₆ it is applied. However, the recrystallization grains of the processed structure are coarsened by the heat treatment, and mechanical properties such as strength and elongation are reduced. The coarsening of the recrystallized grains due to the heat treatment remarkably occurs particularly in the case of forging with a high working ratio of 50% or more.

Therefore, Japanese Patent Application Laid-Open No. 1-283337 proposes to suppress the coarsening of crystal grains by adding Mn, Cr, Zr or the like. Predetermined amount of M
When n, Cr and Zr are added to an Al-Mg-Si-based aluminum alloy in a complex manner, the growth of crystal grains is suppressed in steps such as forging and heat treatment, and a material having a fine crystal structure is obtained. . In Japanese Patent Application Laid-Open No. Hei 3-6346, a forging alloy having the original color tone of an aluminum alloy without discoloration in the forging step and the heat treatment step by adjusting the components such as Si, Cu, Mg, Mn, and Be. Has been introduced.

[0005] Aluminum alloys such as 6010 series
Although it is made into a forging material through an extrusion process, it is inferior in wear resistance and has problems in fastening using bolts and joining with steel members. For example, during use, friction, wear, and the like are generated between the aluminum member and the steel member due to vibration, impact, sliding, and the like, and loosening, falling off, breakage, and the like of the fastening portion are likely to occur. Therefore, there is room for improvement in automotive parts having many bolted portions and the like. To improve wear resistance, the present inventors have found that it is effective to add Sb to an Al-Si alloy and extrude a solidified ingot by a semi-continuous casting method. -268839.

[0006]

The aluminum alloy disclosed in Japanese Patent Application Laid-Open No. 1-268839, in which the structure is refined by adding Sb, is excellent in abrasion resistance, but has a higher tensile strength, fatigue strength and the like than the 6061 alloy. Some problems remain for use as a structural material requiring low strength and high strength.

On the other hand, the aluminum alloy disclosed in JP-A-3-6346 aims at suppressing the discoloration of the surface of a forged product, which is presumed to be caused by the addition of Sb, by adding Be. Insufficient improvement in processability.

[0008] The present invention has been devised to solve such a problem, and includes Si, Sb, Fe, Ti, Mg, and Si.
By balancing the components between B and Cu, the forged T ₆ treated material comparable to the wrought alloy is 33 kg / mm.
^An object of the present invention is to provide an aluminum alloy having a tensile strength of ² or more, and an elongation of 13% or more, which is high in forgeability and wear resistance.

The aluminum alloy for extrusion and forging according to the present invention has an Si content of 3.5 to 6.5% by weight, an Sb content of 0.05 to 0.15% by weight, and an Fe content of 0.2.
5% by weight or less, Cu: 0.5 to 3.5% by weight, Ti:
0.01 to 0.1% by weight, Mg: 0.2 to 0.6% by weight
And B: 0.0005 to 0.02% by weight, with the balance having a substantially Al composition, and
It is characterized in that l ₂ Cu is dispersed and precipitated. This aluminum alloy further contains Mn: 0.05 to 0.5% by weight, Cr: 0.05 to 0.3% by weight, and Sr: 0.00
One or more selected from 1 to 0.05% by weight can be contained.

[0010]

[Action] As shown in FIG. 1, an Al—Si—Mg alloy changes tensile properties such as tensile strength σ _B and elongation δ according to the Si content. That is, when the Si content exceeds 7% by weight, the strength is improved, but the elongation is reduced.
Conversely, if the Si content is less than 4% by weight, the wear resistance is reduced. Further, as shown in Table 1, the elongation tends to increase as the eutectic Si decreases, and is improved by the addition of Sb.

[Table 1]

In the present invention, in order to maintain strength, elongation and wear resistance in the range of Si content of 4 to 7% by weight,
It has been found that the addition of Cu is most effective. The added Cu forms a solid solution in the matrix as it is cast, but forms fine Al ₂ Cu precipitates in the matrix as a result of subsequent processing, heat treatment, etc., and the strength of the aluminum alloy is reduced. And improve hardness.

In this regard, the M used for the same reinforcement is used.
Since g is an element that solid-solution hardens the matrix, unlike Cu, even if strength is improved, elongation and workability are significantly reduced. Therefore, a large amount of Mg cannot be added to an aluminum alloy that requires workability. Further, the added Cu promotes the refining effect of Al-Ti-B even in the ingot state, and also has the effect of suppressing the recrystallized grains after heat treatment from becoming coarse even in an extruded round bar. Thereby, the strength is increased, and a decrease in elongation is prevented.

[0013] As the strength and hardness of the matrix increase, the force for fixing the eutectic Si particles in the matrix, which greatly affects the wear resistance, increases. Therefore, peeling of the eutectic Si particles due to sliding with the counterpart material is prevented, and higher wear resistance is obtained. In addition, the cooling rate of the ingot shifts to the slow cooling side with the addition of Cu, and the time from crystallization of eutectic Si to solidification becomes longer. As a result, eutectic Si
The particles have a rounded shape and a uniform distribution in the ingot. This also improves the wear resistance.

[0014] The addition of Cu has a good effect on the forgeability, and particularly contributes to the reduction of skin roughness, which is one index of deformability. This is not only due to the macro grain refinement effect caused by the addition of Cu, but also to the eutectic Si due to the combined addition of Sb.
This is due to the synergistic effect of (Cu + Sb) in which the effect of refining particles is combined. In addition, the elongation can be improved by the combined addition of Sb.

Hereinafter, the alloy components of the aluminum alloy of the present invention and the content thereof will be described. Si: An alloy element that is effective for imparting good castability and improving wear resistance. 3.5 to Si
The aluminum alloy of the present invention containing 6.5% by weight is advantageous as an automobile part having many bolted portions. Si
If the content is less than 3.5% by weight, not only does the castability deteriorate, but also the strength and wear resistance decrease. On the other hand, 6.5
When a large amount of Si is contained in excess of% by weight, elongation, toughness and the like are deteriorated and forgeability is deteriorated.

Sb: exhibits an effect of making eutectic Si fine, and particularly improves the elongation of an aluminum alloy used for casting and forging. In extrusion and forging,
The solution treatment time can be reduced by adding Sb.
Such an effect of Sb appears remarkably when the content is 0.05% by weight or more. However, the addition of a large amount exceeding 0.15% by weight promotes the generation of brittle intermetallic compounds such as Sb ₂ Mg ₃ and deteriorates the workability of the aluminum alloy. Therefore, the Sb content was set in the range of 0.05 to 0.15% by weight.

Fe: Fe, which is an element mixed into the aluminum alloy as an impurity, becomes an Al—Fe—Si-based compound and is dispersed in the matrix, and has an adverse effect on elongation, toughness, corrosion resistance, and the like. Therefore, the smaller the Fe content, the better. However, excessively lowering the Fe content makes it difficult to melt the alloy. Therefore, Fe
Content is 0.25% by weight with no substantial adverse effect
Has an upper limit.

Cu: an alloy element which plays an important role in the aluminum alloy of the present invention, and improves mechanical strength, wear resistance and the like without lowering elongation. Cu strength improvement by the addition, precipitated by heat treatment such as T ₆ Cu
This is due to Al ₂ . In order to obtain a tensile strength of 33 kg / mm ² or more, it is necessary to contain 0.5% by weight or more of Cu. The strength of the aluminum alloy increases in proportion to the Cu content. However, when the Cu content exceeds 3.5% by weight, the strength improving effect is saturated,
On the contrary, it causes deterioration of corrosion resistance and toughness. Therefore, the Cu content was set in the range of 0.5 to 3.5% by weight.

Ti: It has the effect of making the structure of the ingot fine, preventing cracking of the ingot, and preventing the occurrence of rough surface due to plastic working such as orange peel on the surface of the forged product. Such an effect is remarkably exhibited when 0.01% by weight or more of Ti is contained. However, 0.1
When adding a large amount of Ti exceeding weight%, TiB ₂ ,
Giant crystals, such as TiAl _3, are likely to be generated, causing cracks during forging and surface flaws during cutting. Also,
Deterioration of toughness is also observed due to the large amount of Ti contained. Therefore, the Ti content is determined in the range of 0.01 to 0.1% by weight.

Mg: Similar to Cu, Mg is an essential alloy component for improving the strength of an aluminum alloy. In the aluminum alloy of the present invention to which Mg is added, fine Mg ₂ Si precipitates in the matrix by heat treatment such as T ₆ , and the strength is improved. If the Mg content is less than 0.2% by weight, almost no effect of improving the strength by adding Mg is observed. However, when a large amount of Mg exceeding 0.6% by weight is contained, not only the strength improving effect due to precipitation hardening is saturated, but also crack sensitivity, toughness and the like are reduced, and workability such as extrusion and forging is deteriorated. Therefore, the Mg content is 0.2 to
It was set in the range of 0.6% by weight.

B: Like Ti, it is an effective alloying element for refining crystal grains, and its effect is seen at a content of 0.0005% by weight or more. However, when B is contained in an amount exceeding 0.02% by weight, a large amount of crystallized matter such as TiB ₂ is likely to be generated, and the workability such as forging and cutting is reduced. Therefore, the B content was set in the range of 0.0005 to 0.02% by weight.

The Cr, Mn and Sr added as selective components have the following effects. Cr: An alloy element effective in suppressing the growth of crystal grains during extrusion, forging and subsequent heat treatment, and making the structure after heat treatment fine. This ensures high strength, elongation and toughness. This effect is caused by the presence of 0.05% by weight or more of Cr.
Is remarkable when it is contained. However, if a large amount of Cr is contained in excess of 0.3% by weight, Al—Si—F
The amount of precipitation of hard and brittle intermetallic compounds such as e-Cr-based alloys is increased, and reductions in elongation and toughness, which adversely affect workability, are observed. Therefore, when Cr is contained, its content is determined in the range of 0.05 to 0.3% by weight.

Mn: Like Cr, it is an alloying element that suppresses coarsening of crystal grains and improves strength, elongation, toughness and the like.
The effect of Mn addition becomes remarkable at 0.05% by weight or more.
However, when Mn is contained in an amount exceeding 0.5% by weight, A
The precipitation amount of hard and brittle intermetallic compounds such as l-Si-Fe-Mn system increases, and elongation and toughness, which adversely affect workability, are reduced. Therefore, when Mn is contained, its content is set in the range of 0.05 to 0.5% by weight.

Sr: Like Sb, Sr is an alloy element effective for refining eutectic Si and improving impact value and elongation. Further, it effectively acts to shorten the solution treatment time and improve the forgeability. The effect of such Sr is as follows.
When the content is more than 001% by weight, it appears remarkably. However, 0.0
When Sr is contained in an amount exceeding 5% by weight, the workability is reduced due to the generation of intermetallic compounds, and the incorporation of gas, inclusions, and the like into the molten aluminum is promoted. Therefore,
When Sr is contained, the content is 0.001 to
It is set in the range of 0.05% by weight.

[0025]

EXAMPLE Various aluminum alloys having the components and plasticity shown in Table 2 were melted, and the outer diameter was 325 m by semi-continuous casting.
m, a billet having a length of 600 mm was produced. Table 1
Examples 1 and 2 of the present invention are claims 1 and 2, respectively.
It corresponds to the aluminum alloy specified by. After the obtained billet was kept at 510 ° C. for 4 hours,
The mixture was heated to 50 ° C., and a round bar having a diameter of 45 mm was extruded.

[0026]

[Table 2]

Next, the extruded material was hot forged at a temperature of 450 ° C. and a working ratio of 75%, and subjected to a T ₆ heat treatment. As the T ₆ heat treatment after forging, a heat history of holding at 510 ° C. for 4 hours, cooling with water, leaving at room temperature for 48 hours, and tempering at 170 ° C. for 10 hours was employed. The crystal structure of each heat-treated test piece was observed, and the particle size was measured. In addition, the tensile strength, proof stress and elongation were investigated. Table 3 shows the survey results.

Further, cold forging performed at room temperature and 350 ° C.
The surface roughening phenomenon was observed on the surface of the forged product by an upsetting test by hot forging performed at each temperature of 400 ° C. and 450 ° C., and the forgeability of the extruded round bar was evaluated based on the quality. As the test piece used at this time, an extruded round bar was held at 410 ° C. for 1 hour for a cold forging test, and then annealed material was gradually cooled. For a hot forging test, an extruded round bar was used. It was used. In each test, a cylindrical test piece having a diameter of 14 mm and a height of 26 mm cut from an extruded round bar was used. These test pieces were compressed to a thickness of 5 mm at a speed of 100 mm / sec using a 25-ton hydraulic electric servo pulser testing machine, and the roughened surface of the measurement surface was observed at a processing rate (upsetting rate) of 80%. . Recrystallization was promoted by the upsetting forging, and coarse recrystallized grains of 400 to 500 μm were generated. However, in the alloys of the present invention, fine recrystallized grains of 150 to 350 μm were used. It was effectively suppressed.

Table 3 also shows the observation results of the surface condition.
In Table 3, ◎ indicates that the measured surface of the forged product was smooth and maintained the metallic luster, ○ indicates that the forged product was slightly uneven, but the metallic luster was maintained, and irregularities were generated all around. The sample was evaluated as △, the sample having large depths of irregularities and losing metallic luster was evaluated as ×, and the sample having many irregularities and a large step was evaluated as XX.

[0030]

[Table 3]

As is clear from Table 3, the aluminum alloys of Examples 1 and 2 of the present invention both have a high tensile strength of 33 kgf / mm ² or more, have a fine crystal structure after forging, and have a rough appearance. None of them exhibited. This is presumed to be due to the synergistic effect of Sb and Cu. That is, the eutectic Si is refined by the addition of Sb, and the refinement effect of the Al-Ti-B-based intermetallic compound is promoted by the addition of Cu, and these provide a synergistic mechanical property and workability. Can be In addition, the decrease in elongation δ is small, and the proof stress σ _0.2 is significantly improved.

On the other hand, in comparative alloys 7 and 9, Cu
No strength was obtained due to no addition.
-The roughening of the forged product is severe due to the absence of Ti-B and Cu. In the comparative alloy 10, Sb and C
Since u was not added, the eutectic Si and the macroparticles as recrystallized grains were both coarse, and were inferior to the alloy of the present invention in all points of strength, elongation, and surface roughness.

In the wear resistance evaluation test, a dry Ogoshi type testing machine was used, and a rotating disk of FC28 was used as a mating material. Then, a load of 2.1 kg and a friction speed of 1.21 m /
The test piece was rubbed against the mating material at a speed of 2.24 m / sec and 3.88 m / sec, and the amount of the test piece scraped off by the rotating disk of FC28 was calculated. The calculation results are shown in Table 4.

[Table 4]

As is clear from Table 4, the alloy of the present invention of Test No. 2 has a smaller amount of wear and a wear resistance of 6 in all speed ranges as compared with the alloy of Test No. 9 containing no Cu. It can be seen that it has been improved by ~ 22%. The main reasons why the wear resistance is improved are the following two. The addition of Cu increases the hardness and strength of the matrix, and as a result, increases the force for fixing eutectic Si, which has the greatest effect on wear resistance, and prevents peeling due to friction. The addition of Cu lowers the solidification rate and slows the cooling, so that the effect of Al-Ti-B is more remarkably exhibited, and the crystal grains of the ingot are refined and uniformized. The eutectic Si itself solidified in the boundary is also rounded in shape and has a uniform distribution.

[0035]

As described above, in the present invention, the crystal grain refining action by Sb, Ti, B, etc.
Utilization of matrix reinforcement by u, Mg, etc., and adoption of an alloy design that balances these alloy components, excels in extrudability and forgeability, as well as good surface roughness resistance and mechanical properties. We have obtained aluminum alloys for extrusion and forging. Since this aluminum alloy has significantly improved tensile strength, proof stress, and the like as compared with conventional aluminum alloys for forging, it is suitable as a structural material for automobiles having many bolted portions, for example.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of Si content on the tensile strength and elongation of an Al—Si—Mg based alloy.

Continuation of the front page (56) References JP-A 1-268839 (JP, A) JP-A 3-166333 (JP, A) JP-A 63-259045 (JP, A)

Claims (4)

(57) [Claims] 1. Si: 3.5 to 6.5% by weight, Sb:
0.05 to 0.15 wt%, Fe: 0.25 wt% or less, Cu: 0.5 to 3.5 wt%, Ti: 0.01 to
0.1% by weight, Mg: 0.2-0.6% by weight and B:
Extrusion / forging characterized by containing 0.0005 to 0.02% by weight, with the balance having a substantially Al composition and fine Al ₂ Cu dispersed and precipitated in the matrix after T6 treatment. Aluminum alloy. 2. Si: 3.5 to 6.5% by weight, Sb:
0.05 to 0.15 wt%, Fe: 0.25 wt% or less, Cu: 0.5 to 3.5 wt%, Ti: 0.01 to
0.1% by weight, Mg: 0.2-0.6% by weight, B: 0.
0005-0.02% by weight, and further Mn: 0.05
To 0.5% by weight and / or Cr: 0.05 to 0.3% by weight
% . The aluminum alloy for extrusion and forging, characterized in that the balance has a substantially Al composition and fine Al ₂ Cu is dispersed and precipitated in the matrix after T6 treatment. 3. Si: 3.5 to 6.5% by weight, Sb:
0.05 to 0.15 wt%, Fe: 0.25 wt% or less, Cu: 0.5 to 3.5 wt%, Ti: 0.01 to
0.1% by weight, Mg: 0.2-0.6% by weight, B: 0.
0005-0.02% by weight, and Sr: 0.00
1 to 0.05% by weight , with the balance having a substantially Al composition, and a fine Al ₂ C
An aluminum alloy for extrusion and forging, wherein u is dispersed and precipitated. 4. Si: 3.5 to 6.5% by weight, Sb:
0.05 to 0.15 wt%, Fe: 0.25 wt% or less, Cu: 0.5 to 3.5 wt%, Ti: 0.01 to
0.1% by weight, Mg: 0.2-0.6% by weight, B: 0.
0005-0.02% by weight, and further Mn: 0.05
To 0.5% by weight and / or Cr: 0.05 to 0.3% by weight
% And Sr: 0.001 to 0.05 % by weight , with the balance having a substantially Al composition, and fine Al ₂ Cu dispersed and precipitated in the matrix after T6 treatment. Aluminum alloy for extrusion and forging.